Dies and roll manufacture by electroerosion

ABSTRACT

A METHOD OF FORMING A TUBE REDUCING TOOL COMPRISING THE STEP OF FORMING A TOOL BLANK OF STEEL HAVING A ROLL PORTION AND DRIVE SHAFT PORTION. THE ROLL PORTION IS PROCESSED TO FORM A SERIES OF SPACED ROLL BLANKS ALONG THE LENGTH OF THE TOOL WHICH IS THEN HEAT TREATED TO A HARDENED STATE. THEREAFTER, ELECTRODES ARE POSITIONED IN THE LATERAL TANGENCY TO AND GENERALLY BESIDE THE STELL ROLL BLANKS TO BE MACHINED. THE ELECTRODES ARE THEN CAUSED TO EMIT AN ELECTRICAL SPARK DISCHARGE WHILE CAUSING A TANGENTIAL SURFACE OF THE ROLL BLANKS TO MOVE ALONG THE LENGTH OF THE ELECTRODES ESTABLISHING A CUTTING ZONE ALONG THE TANGETIAL SURFACES OPPOSED TO THE ELECTRODES FORMING TAPERED GROOVES EXTENDING GENERALLY IN ARCUATE DIRECTIONS THEREIN.

Feb. 9, 1971 M. J. CELOVSKY 3,562,702

DIES AND ROLL MANUFACTURE BY ELECTROEROSION Original Filed Sept. 13, 1965 7 Sheets-Sheet l 2/ Fig.1

.53 4/ 4 Z6 Z6 32 F g Z INVENTOR.

BY ATTORNEYS Feb. 9, 1971 M. J. CELOVSKY I 3,562,702

DIES AND ROLL MANUFACTURE BY ELECTROEROSION Original Filed Sept. 13, 1965 7 Sheets-Sheet 2 IN VENTOR.

B Y A'I'V'ORNIiYS DIES AND ROLL MANUFACTURE BY ELECTROEROSION Original Filed Sept. 13, 1965 Feb. 9, 1971 M. J.- CELOVSKY 7 Sheets-Sheet 5 INVENTOR. C'e/a V31 ATTORNEYS DIES AND ROLL MANUFACTURE BY ELECTROEROSION Original Filed Sept. 13, 1965 Feb. 9, 1971 M. .1. CELOVSKY 7 Sheets-Sheet 4 m w m N 1 M/bhae/ Cle/ouzsuy w 9 ATTORNEYS Feb. 9, 1971 M. J. CELQVSKY 3,562,702

DIES AND ROLL MANUFACTURE BY ELECTROEROSION Original Filed Sept. 13, 1965 7 Sheets-Sheet 6 DIES AND ROLL MANUFACTURE BY ELECTROEROSION Original Filed Sept. 13, 1965 Feb. 9, 1971 M. J. CELOVSKY 7 Sheets-Sheet '7 INVENTOR. C'e/omsly M'c-bae/ d ATTORNEYS United States Patent O 3,562,702 DIES AND ROLL MANUFACTURE BY ELECTROEROSION Michael J. Celovsky, Detroit, Mich., assignor to Industrial Tool Engineering Company, Detroit, Mich., a corporation of Michigan Original application Sept. 13, 1965, Ser. No. 486,652, now Patent No. 3,435,174, dated Mar. 25, 1969. Divided and this application Oct. 17, 1968, Ser. No. 785,425 The portion of the term of the patent subsequent to Sept. 15, 1981, has been disclaimed Int. Cl. 1323p N08 US. Cl. 219-69 7 Claims ABSTRACT OF THE DISCLOSURE A method of forming a tube reducing tool comprising the step of forming a tool blank of steel having a roll portion and drive shaft portion. The roll portion is processed to form a series of spaced roll blanks along the length of the tool which is then heat treated to a hardened state. Thereafter, electrodes are positioned in lateral tangency to and generally beside the steel roll blanks to be machined. The electrodes are then caused to emit an electrical spark discharge while causing a tangential surface of the roll blanks to move along the length of the electrodes establishing a cutting zone along the tangential surfaces opposed to the electrodes forming tapered grooves extending generally in arcuate directions therein,

This invention relates to a method for electrically inachining heat treated or hardened metals and in particular to a device for tapering arcuate grooves in a tube reducing roll after the final heat treating process.

The present application is a divisional of my co-pending application entitled Electrical Discharge Machining Apparatus, Ser. No. 486,652, filed Sept. 13, 1965.

Recently, means have been developed for electrically machining tube reducing rolls to a high finish by passing an energized electrode adjacent to the moving surface of a rotating roll and utilizing and erosive effect of the resulting electrical discharge.

While direct electrical machining has appreciably improved the efficiency of prior hand finishing methods, devices currently used for this purpose have not been entirely satisfactory. For instance, heretofore machines have been equipped for machining a single set of tube reducing rolls. The machining process consists of passing a tapered electrode into the path of synchronously rotating rolls for the purpose of conforming roll grooves to the configuration of the electrode. The electrical erosion relied upon to achieve this objective is a comparatively slow process. Therefore, it would be highly desirable to construct an apparatus for machining several sets of rolls during a single synchronous stroke of the machine.

Also, the manner of mounting the individual rolls for machining has been found to be time consuming and to involve unnecessary cost. Previously individual rolls have been provided with a central bore for being mounted on a shaft or spindle of the electrical discharge machine. This form of mounting has been necessitated by the requirement that the spindle of the electrical discharge machine be permanently geared to the movement of the associated tapered electrodes. Nevertheless, it has been recognized that providing a device for finish machining an integral roll and shaft combination would be highly desirable.

It is a principle object of this invention to provide a new and improved method for manufacture of dies and rolls, more particularly this method involves the steps of producing a plurality of tube reducing rolls simultaneously. In the preferred form of the invention, the method contemplates the formation of the tapered rolls integral with the drive shaft or spindle. The electrical discharge machining of the tapered rolls takes place in a fluid bath and involves electric spark burning of the material whereby the roll grooves are accurately reshaped to desired dimensions. Considerable advantage can be obtained in a process of this type since the grooves on the rolls can be machined to shape where the rolls are manufactured from work hardened steel or tool steel without impairing the metallurgical character of the steel. Conventionally, these grooves had been formed to shape in so called soft steel and then the rolls would be individually heat treated and in the subsequent heat treating process the critical dimensional characteristics of the grooves would be frequently impaired. The basic method and apparatus for machining rolls of the type herein disclosed is the subject of a number of U8. patents previously granted to the Applicant including US. Pat. No. 3,148,446.

These and other objects, features and advantages of the present invention will be understood in greater detail from the following description and the associated drawings wherein reference numerals are utilized in designating a preferred embodiment and wherein:

FIG. 1 is an elevated view of a roll and spindle blank utilized in forming the tube reducing tool of the present invention;

FIG. 2 is also an elevational view showing an intermediate stage in the production of the tube reducing tool of this invention;

FIG. 3 is a view similar to that shown in FIG. 2 incorporating the additional features of machined keyways and relief pockets;

FIG. 4 is a sectional view taken along the line IVIV of FIG. 3 illustrating the geometry of the relief pocket utilized in the tube reducing tool of this invention;

FIG. 5 is a further sectional view taken along the lines V-V of FIG. 3 and showing the relationship of the diametrically opposed keyways as employed in the tool of this invention;

FIG. 6 is an elevational view of the tube reducing tool of this invention after the final machining process to be described herein;

FIG. 7 is a rear elevational view of the electrode machining device of this invention emphasizing the electrode carriage structure and the longitudinal orientation of the tube reducing tool as shown in FIG. 6;

FIG. 8 is an enlarged end view of the electrode machining device of this invention illustrating the novel roller support means for the tube reducing tool shown in FIG. 6 and also illustrating the geared relationship between the electrode carriage structure and the rotating roll spindles;

FIG. 9 is a top view of the electrode machining device of this invention illustrating the functioning of the plural electrode structure in penetrating the tapering grooves of adjacently disposed tube reducing rolls;

FIG. 10 is a sectional view of the electrode machining device of this invention as taken along the lines XX of FIG. 7 illustrating the relationship of the hydraulic carriage mechanism and the supporting structure for the tapered electrodes as well as the configuration of the fiuid bath tank;

FIG. 11 is a further sectional view of the electrode machining device of this invention as taken along the lines XIXI of FIG. 7 illustrating the carriage structure and the oil reservoir system;

FIG. 12 is a partially sectioned view as taken along the lines XII-XII of FIG. 8 for illustrating the structure and function of the readily removable gearing means employed for driving the tube reducing shaft of this invention;

FIG. 13 shows an octagonal seal ring utilized in conjunction with the fluid bath of this invention and further indicated in FIGS. and 11; and

FIG. 14 is a sectional view taken along the lines XIV- XIV of FIG. 7 showing the operation of the novel locking mechanism as applied to the carriage structure of this invention.

AS SHOWN ON THE DRAWINGS The sequence of manufacturing operations for a preferred embodiment of this invention is shown generally in FIGS. 1 through 6. In FIG. 1 a blank is provided with a roll portion 21 and drive shaft or spindle portion 22. The roll portion 21 is rough machined to define a series of rolls 23, 24 and 25. The rolls 23, 24 and 25 consist of pairs of collars or ridges 26 and 27 extending above radially reduced regions 28, 29', 30 and 31. A rough machined arcuate groove 32 is formed between the ridges 26 and 27 and provides the principal tube reducing surface. The shaft or spindle 22 is similarly machined and is provided with a series of decreasing diameters 33, 34, 35 and 36 for meeting various functional requirements of a tube reducing machine.

After completion of the machining processes indicated in FIG. 2, the tube reducing tool is provided with keyways 37 and 38, as shown in FIGS. 3 and 5, and relief pocket 39 illustrated in FIG. 4. Finally, the tube reducing tool is finish machined by the electrode machining device of this invention. The result is shown in FIG. 6 and takes the form of tapered walls 40 and 41 provided at the inner surface of the grooves 32. The tapered walls 40 and 41 allow for the gradual compressing of a reducible tube as is Well understood in the art.

FIGS. 7 through 14 illustrate various features of the electrode cutting machine of this invention, and, in particular, FIGS. 7, 8 and 9 collectively illustrate the mounting of the tube reducing tools on the machine structure.

Referring to FIGS. 7, 8 and 9, tube reducing shafts 42 and 43 are deployed in side-by-side relationship on a bed 44 of the electrode cutting machine.

The shafts 42 and 43 are supported on sets of rollers 45 and 46 disposed at opposite ends of the bed 44. The roller sets 45 and 46 consist of cylindrical rollers 47 freely mounted for rotation at a vertical supporting fixture 48. As in FIG. 8, the rollers 47 are rotatably supported at points 49, 50, 51 and 52 on the bracket 48 so as to provide correct spacing of the shafts 42 and 43 carried thereon.

While the spacing between the shafts 42 and 43 is provided by the positioning of the roller sets 45 and 46, the axial alignment of the shafts and hence of the individual rolls is accomplished by end fixtures 53 which are bolted to the bed 44 as at 53a. The fixtures 43 are provided with an axially adjustable guide arm 54 for establishing the desired orientation of the associated shaft. Fine adjustment of the end fixture 53 is accomplished through the use of an eccentric plug 55 which interconnects the base 56 of the fixture 53 and the body of the bed 44. By turning a screw 57 the relative positioning of the fixture 53 and the bed 44 can be altered, as is well understood.

With the shafts 42 and 43 properly mounted on the bed 44, means must be provided for passing an electrode within the grooves 32 and for synchronously rotating the associated shafts for tapering the individual rolls in accordance with the requirements of tube reducing machines.

To produce proper movement of the electrode cutters a hydraulically operated carriage system is provided at the rear of the bed 44. The carriage system consists of a carriage head 58 supported and operated by a conventional hydraulic mechanism 59. The hydraulic mechanism 59 consists of a hydraulic cylinder 60 and a relatively extensible power member 61. Fluid pressure is applied to the cylinder 60 through a pressure inlet 61 conducting from a fluid pump or the like. Fluid pressure within the cylinder 60 acts on a piston attached to the extensible rod 61 for raising or lowering the carriage head 58 in accordance with the demands of the fiuid control system. The cylinder 60 is mounted to the bed 44 through the provision for an outer housing 62. In particular, the cylinder 60 is secured to the housing 62 at'a plurality of bolts 63, while the housing 62 is mounted to the bed 44 by fasteners 64. In a similar manner the upper extremity of the rod 61 is secured to the carriage head 58.

The carriage head 58 is principally supported by the relatively extensible rod 61. However, similarly extensible guide columns 65 and 66 provide stability to the movement of the carriage assembly. The guide columns 65 and 66 are slidably received within cylindrical supports 67 and 68, which are in turn fixedly secured to the bed 44 at a plurality of lugs 69. The carriage head 58 is received about the upper extremity of the columns 65 and 66 within cylindrical casings 70 and 71. Similarly, a carriage base 72 is provided with cylindrical casings as shown at 73 which are fixedly mounted about the lower extremity of the columns 65 and 66. Therefore, the movement of the relatively extensible hydraulic rod 60 operates the assembly of the guide columns 65 and 66 and their associated head and base 58 and 72, respectively.

A principal function of the carriage assembly is to pass a series of electrodes between the shafts 42 and 43 for tapering the roll grooves 32. To accomplish this purpose the carriage unit is provided with upper and lower cantilever arms 74 and 75 for supporting electrode pins 76 and 77. The pin 76 is formed integrally with a threaded stud 78 which is mounted to the cantilever arm 74 for being axially adjustable by rotation of the positioning wheel 79. In contrast, the pin 77 is affixed to a shaft 80 which is mounted to the lower cantilever arm 75 in a suitable manner for being substantially axially stationary.

A series of tapered electrodes 81 are securely positioned between the pins 76 and 77 by the tightening of the wheel 79. It is appreciated, therefore, that the electrodes 81 will be caused to move in a vertical path with the carriage assembly according to the dictates of the hydraulic mechanism 59. It is this movement of the electrodes 81 that performs the electrical machining action desired by this invention.

To produce a tapered groove due to the vertical motion of the tapered electrodes 81 the shafts 42 and 43 must rotate into the path of the descending or ascending electrodes. Furthermore, this rotation must be synchronized to the movement of the shaft in order to produce the desired consistent taper within the grooves 32.

Synchronization is accompanied by gearing the upward or downward progession of the carriage assembly directly to the shafts as seated on the support rollers 47. Three gearing elements are utilized to accomplish this objective. First, a rack gear 82 is fixedly mounted via a bolt 83 within a cooperable casing 84 formed integrally with the carriage head 58. Second, a pinion gear 85 is rotatably mounted on a support bracket 86 which in turn is rigidly secured about the adjacent shaft 42.

As shown in FIG. 8, vertical motion of the carriage assembly and, therefore, of the rack gear 82 will be converted to a rotary motion through the pinion 85 to the ring gears 87 and 88 and hence to the shafts 42 and 43. It may be noted that the rack gear 82 is maintained in mesh with the pinion 85 during its vertical progression by a guide wheel 89 rotatably mounted on the fixture 86 which also supports the pinion 85. It can be understood, therefore, that the shafts 42 and 43 through the provision for the interlocking gearing system are positionally related to the progression of the carriage assembly, which is the desired consequence for producing the tapered grooves of the tube reducing rolls.

Since the tube reducing roll as shown in FIG. 6 comprises a plurality of rolls which are mounted on an integral shaft, the ring gears 87 and 88 must be applied to each set of shafts to be finish machined.

To improve the efficiency of the application of the ring gears to the shafts 42 and 43 a novel gearing assembly has been employed in this electrode cutting machine. In particular, FIG. 12 shows a cutaway portion of the ring gear assembly as indicated in FIG. 8. The ring gear 88 is provided to be slidably received over the shaft 42 at the diameter 28 and a split ring 90 is likewise slipped over the shaft 42 for abutting the edge '91 of the gear 88. The split ring 90 is separable at faces 92 and 93 and, therefore, is easily expandible about the shaft surface 28. With the ring gear 88 and the split ring 90 in abutment thereto, the ring 90 is fixedly secured to the gear 88 by a plurality of peripheral bolts 94. Finally, the assembled unit of the split ring and ring gear are bound to the shaft 42 by constricting the split ring about the surface 28. This constriction is accomplished by tightening a pair of screws 95 and 96 which cooperatively close the gap between the opened edges 92 and 93. The screws 95 and 96 may be adjusted by a standard screwdriver or similar applicable wrench through the openings 97 and 98. Through this provision for readily removable gearing, the shafts 42 and 43 remain untouched and the machine set-up time is significantly reduced.

To accomplish the electrical machining of the grooves 32 associated with the rolls of the shafts 42 and 43 a continuous fluid bath must be provided about the electrical cutting surfaces. A tank is provided centrally of the bed 44 to engulf the cutting regions of the shafts 42 and 43. The oil tank 99 is provided with longitudinal side walls 100 and end walls 101. The end walls 101 have shaft openings 102 which permit the extension of the shafts to points externally of the oil tank where support and rotation can be more adequately applied.

To assure a steady supply of oil to the cutting surfaces an oil seal must be mounted about the shafts 42 and 43. This seal takes the form of a ring 103 shown in FIG. 13 as having an octagonal outer periphery 104 and a circular inner diameter 105. The octagonal outer surface 104 is provided with radial notches 106 as a means of fastening the ring 103 to the end wall 101 of the oil tank 99. The shaft opening 102 of the end wall 101 has a configuration which is complementary to the octagonal outer periphery of the ring 103.

As shown in FIGS. and 11 a pair of seal rings 103 may be fitted within the complementary shaft openings 102 to provide a tight and effective seal for the tank 99. In particular, the seal ring 103 is fastened to the end wall 101 at a plurality of points 107 and to each other at the points 108 and 109. To provide an effective seal between the end wall 103 and the rotating shafts 42 and 43, an O-ring 110 is fitted at the inner surface of the seal 103, and is shown in both FIGS. 12 and 13.

As shown in FIG. 11, the oil tank 99 is communicable with a lower chamber 111 formed by chamber walls 112 extending about the lower cantilever arm 72 of the carriage system. The chamber 111 is tapped at a point 113 and an outlet nozzle 114 with an associated valve 115 is mounted thereto to permit effective draining of the tank 99.

During the progression of the tapered electrodes 81 within the grooves 32 of the associated rolls it may be desirable for a variety of mechanical reasons to hold the position of the carriage system. Also, it may be desirable for locking the carriage assembly in an elevated orientation in the absence of fluid pressure within the hydraulic system.

To accomplish either of these objectives, a locking device is provided directly about the guide columns 65 and 66 and is best illustrated in FIG. 14 of the drawings. In FIG. 14 a chain or cable 116 is deployed about the column 65 within the guide cylinder 67. The cable 116 has a first end 117 locked within the guide cylinder 67 at a pair of set screw ball joints 118 and 119. By turning the set screws 118 and 119 the balls 120 and 121 are forced to crimp-lock the cable end 117.

The opposite end of the cable 16 extends through a slot 122 formed within the cylindrical support 67 to a lug 123 securely clamped to the cable extremity. A locking arm 124 is pivotally supported to a bracket 125 at a point 126. The bracket 125 is rigidly supported to the cylindrical support 67, and the arm 124, when pivoted about the bracket 125, increases the tension on the cable 116 for grasping or clamping the guide column 65. To accomplish this tensioning of the cable 116 a lever 127 is utilized in conjunction with an eccentric cam 128. In particular, the cam 128 is rotatably positioned about the extremity of the arm 124- at a point 129 and is provided to ride against the outer surface of the cylindrical support 67 at a point 130. By movement of the lever 127 the distance between the pivot 129 and the outer surface of the support cylinder 67 can be varied due to the eccentric nature of the cam 128. This corresponds to a pivotal movement of the locking arm 124 and, hence, to a tensioning of the cable 116.

METHOD OF FORMING THE TUBE REDUCING TOOL With regard to the method, it will be appreciated that the blank 20 is formed of a single piece of forged steel having the roll portion 21 and the drive shaft portion 22 which extends at opposite ends of the roll portion. The blank is then further processed or machined to form the rolls or roll blanks 23, 24, 25 and the grooves 32 are rough machined therein.

The relief pockets 27 and the keyways 38 are then formed in the grooves 32 and in the drive shaft portion 22 and the drive shaft portion is machined to form a series of decreasing diameters 33, 34, 35 and 36. The tool is then heat treated into a hardened state. The order of the steps up to the heat treating step can be varied as required.

The tool is then positioned in adjacency to the tapered electrodes such as the electrode 81 in such a way that the electrodes'are aligned with the grooves 32. Relative movement is then brought about between the electrode and the roll blanks and an electric spark is caused to be discharged by the electrodes to establish a cutting zone whereby the taper is burned into the grooves 32. During the burning operation, the cutting zone is immersed in oil. In the illustrated embodiment, the electrodes are caused to move tangentially of the grooves 32 in an upward direction so that machined particles can fall away from the cutting zone to minimize short circuits. The electrodes can be mounted in such a position as to be positioned over the grooves and then caused to move in a downward direction to machine the grooves, but better results are obtainable where the electrodes are positioned so as to underlie the grooves being machined.

After the grooves have been machined to impart the desired taper to them no further heat treatment is required and the grooves can then be polished to provide the desired micro-finish thereon.

It will be understood that various modifications may be suggested by the embodiments dislosed, but I desire to claim within the scope of the patent warranted hereon, all such modifications as come within the scope of my invention.

I claim as my invention:

1. A method of forming a tube reducing tool comprised of a single piece of steel which comprises:

forming a blank with a roll portion and a drive shaft portion,

rough forming spaced roll blanks in the roll portion along the length of the tool,

heat treating the steel tool into a hardened state, and

contemporaneously burning circumferentially tapered arcuate grooves in radially outer surfaces of the heat treated hardened roll blanks with an electric spark discharge in a fluid bath whereby the tapered arcuate grooves are formed to shape without the impairment of heat treatment characteristic of the steel.

2. A method of forming a tube reducing tool comprising the steps of:

forming a one-piece forging have a drive shaft portion and a roll portion, rough machining the roll portion to form a series of roll blanks spaced along the length of the drive shaft portion, rough forming grooves in the perimeter of the roll blanks, heat treating the tool, and turning the tool while upwardly moving tapered electrodes tangentially of the roll blanks and electric spark contemporaneously burning tapered grooves in the roll portions while the cutting zone is immersed in oil to permit thus machined particles to fall away from the cutting zone to minimize short circuits. 3. In a method of manufacturing a tube reducing tool by the use of electrical discharge electrodes each having a longitudinally tapered smooth uninterrupted outer surface corresponding to the configuration to be machined in the metal roll, the steps of:

forming a one-piece tool blank comprised of steel having a roll portion and a drive shaft portion,

processing the roll portion to form a series of spaced roll blanks along the length of the one-piece tool,

heat treating the tool into a hardened state,

positioning the electrodes in lateral tangency to and generally beside the steel roll blanks to be machined, and

contemporaneously energizing the electrodes causing the tapered electrodes to emit an electrical spark discharge while causing a tangential surface of the roll blanks to move along the length of the electrodes establishing a spaced cutting zone along the tangential surfaces opposed to the electrodes contemporaneously forming tapered grooves extending generally in arcuate directions therein.

4. A method of forming a tube reducing tool comprised of a single piece of steel which comprises:

forming a blank with a roll portion and a drive shaft portion,

rough forming spaced roll blanks in the roll portion along the length of the tool,

machining opposite ends of the drive shaft portion, forming a series of decreasing diameters on the drive shaft portion at opposite ends of the roll portion,

cutting keyways in the drive shaft portion,

heat treating the tool steel into a hardened state, and

contemporaneously burning circumferentially tapered arcuate grooves in radially outer surfaces of the heat treated hardened roll blanks with an electric spark discharge in a fluid bath whereby the tapered arcuate grooves are formed to shape without the impairment of heat treatment characteristic of the steel.

5. A method of forming a tube reducing tool comprised of a single piece of steel which comprises:

forming a blank with a roll portion and a drive shaft portion,

rough forming spaced roll blanks in the roll portion along the length of the tool,

machining opposite ends of the drive shaft portion,

forming a relief pocket in each of the roll blanks,

heat treating the tool steel into a hardened state, and

contemporaneously burning circumferentially tapered arcuate grooves in radially outer surfaces of the heat treated hardened roll blanks with an electric spark discharge in a fluid bath whereby the tapered arcuate grooves are formed to shape without the impairment of heat treatment characteristic of the steel.

6. A method according to claim 2 wherein the step of turning includes supporting the tool at the shaft portion and applying a turning force thereto.

7. A method according to claim 5 wherein said step of burning includes rotating said tool on its axis by supporting each of said ends of the drive shaft portions and applying a rotational force thereto.

References Cited UNITED STATES PATENTS 2,121,435 6/1938 Koehler 51289X 2,195,064 3/1940 Wallace 5l-289X 3,067,317 12/1962 Buro 21969V 3,148,446 9/1964 Celovsky 2l9-69E 3,149,218 9/1964 Celovsky 219-69V 3,275,788 9/1966 Ferguson 21969V RALPH F. STAUBLY, Primary Examiner U.S. Cl. X.R. 51-289 

